[linux-lvm] Snapshot causing segault

Thu Jan 3 13:25:49 UTC 2013

On Thu, Jan 3, 2013 at 5:18 AM, Zdenek Kabelac <zkabelac at redhat.com> wrote:

> Dne 31.12.2012 19:50, Tyler Gates napsal(a):
>
>  Hello everyone,
>>       I've been having an intermittent problem on random servers
>> segfaulting
>> while trying to create a snapshot under version  lvm2-2.02.17-7.38.3 on
>> kernel 2.6.16.60-0.93.1-bigsmp (SLES 10 SP4). The messages I get are:
>> ##############################**#############
>> Dec 27 07:45:39 chelco-app-01 kernel: Unable to handle kernel NULL pointer
>> dereference at virtual address 0000001c
>> Dec 27 07:45:39 chelco-app-01 kernel:  printing eip:
>> Dec 27 07:45:39 chelco-app-01 kernel: f90ab3a7
>> Dec 27 07:45:39 chelco-app-01 kernel: *pde = 3780a001
>> Dec 27 07:45:39 chelco-app-01 kernel: Oops: 0000 [#1]
>> Dec 27 07:45:39 chelco-app-01 kernel: SMP
>> Dec 27 07:45:39 chelco-app-01 kernel: last sysfs file:
>> /devices/pci0000:00/0000:00:**02.0/0000:04:00.1/irq
>> Dec 27 07:45:39 chelco-app-01 kernel: Modules linked in: raw dock button
>> battery ac loop dm_snapshot usbhid dm_mod uhci_hcd bnx2x hw_random
>> ehci_hcd
>> qla2xxx hpilo usbcore firmware_class scsi_transport_fc parport_pc lp
>> parport
>> ext3 jbd edd
>> fan thermal processor cciss sd_mod scsi_mod
>> Dec 27 07:45:39 chelco-app-01 kernel: CPU:    4
>> Dec 27 07:45:39 chelco-app-01 kernel: EIP:    0060:[<f90ab3a7>]
>>  Tainted: G
>>      X VLI
>> Dec 27 07:45:39 chelco-app-01 kernel: EFLAGS: 00210202
>> (2.6.16.60-0.93.1-bigsmp #1)
>> Dec 27 07:45:39 chelco-app-01 kernel: EIP is at __map_bio+0x50/0x11f
>> [dm_mod]
>> Dec 27 07:45:39 chelco-app-01 kernel: eax: f90960c4   ebx: 00000000   ecx:
>> f7ff2a60   edx: f7794440
>> Dec 27 07:45:39 chelco-app-01 kernel: esi: f7ff2a58   edi: f90960c4   ebp:
>> f46306c0   esp: f4c15d28
>> Dec 27 07:45:39 chelco-app-01 kernel: ds: 007b   es: 007b   ss: 0068
>> Dec 27 07:45:39 chelco-app-01 kernel: Process lvcreate (pid: 6678,
>> threadinfo=f4c14000 task=f7838680)
>> Dec 27 07:45:39 chelco-app-01 kernel: Stack: <0>f7794340 f7794440 f7794440
>> 03201ff0 00000000 03201ff0 00000000 00000008
>> Dec 27 07:45:39 chelco-app-01 kernel:        00000000 00000000 f90960c4
>> f7ff2a68 f46306c0 f90abd1b 00000000 00000001
>> Dec 27 07:45:39 chelco-app-01 kernel:        00000008 f428e2e0 fcdfe010
>> ffffffff c0113d62 00000000 0000001f f7ff2a58
>> Dec 27 07:45:39 chelco-app-01 kernel: Call Trace:
>> Dec 27 07:45:39 chelco-app-01 kernel:  [<f90abd1b>]
>> __split_bio+0x182/0x440
>> [dm_mod]
>> Dec 27 07:45:39 chelco-app-01 kernel:  [<c0113d62>]
>> do_flush_tlb_all+0x0/0x5d
>> Dec 27 07:45:39 chelco-app-01 kernel:  [<f90abff0>]
>> __flush_deferred_io+0x17/0x20 [dm_mod]
>> Dec 27 07:45:39 chelco-app-01 kernel:  [<f90ac14c>] dm_resume+0x8e/0xf9
>> [dm_mod]
>> Dec 27 07:45:39 chelco-app-01 kernel:  [<f90aedd8>]
>> dev_suspend+0x138/0x157
>> [dm_mod]
>> Dec 27 07:45:39 chelco-app-01 kernel:  [<f90af607>] ctl_ioctl+0x220/0x26e
>> [dm_mod]
>> Dec 27 07:45:39 chelco-app-01 kernel:  [<f90aeca0>] dev_suspend+0x0/0x157
>> [dm_mod]
>> Dec 27 07:45:39 chelco-app-01 kernel:  [<c0179ce8>] do_ioctl+0x48/0x5e
>> Dec 27 07:45:39 chelco-app-01 kernel:  [<c0179f60>] vfs_ioctl+0x262/0x275
>> Dec 27 07:45:39 chelco-app-01 kernel:  [<c0179fc7>] sys_ioctl+0x54/0x6d
>> Dec 27 07:45:39 chelco-app-01 kernel:  [<c0103dcb>]
>> sysenter_past_esp+0x54/0x79
>> Dec 27 07:45:39 chelco-app-01 kernel: Code: b4 0a f9 89 70 40 8b 06 83 c0
>> 0c
>> f0 ff 00 8b 54 24 08 8d 4e 08 8b 02 8b 52 04 89 44 24 0c 89 f8 89 54 24
>> 10 8b
>> 5f 04 8b 54 24 08 <ff> 53 1c 83 f8 00 89 c2 0f 8e 93 00 00 00 8b 54 24 08
>> 8b 42 0c
>> ##############################**##############################**#
>>
>> The result is the target volume gets suspended and the only way to fix it
>> is
>> to reboot and remove the faulty snapshot when it comes back up.
>>
>> Now the script I wrote that creates these snapshots will use all available
>> extents from the Volume Group pool which in this case was actually larger
>> than
>> the size of the volume I was trying to snapshot. Thinking this was the
>> problem, I tried creating the snapshot several times using a snapshot size
>> less than or equal to the target volume and it worked every time. So, I
>> tried
>> a value larger than the target to generate a crash and it did BUT not
>> every
>> time. In fact now I can't get it to segfault at all.
>>
>> So my question is: is creating the snapshot volume with a size larger
>> than the
>> target volume inducing segfaults randomly or could there be another
>> problem
>> lurking? If these weren't production machines I would normally just go
>> with a
>> size smaller than the target but I really need to be sure what exactly is
>> causing the segfaults.
>>
>> Any help would be appreciated.
>>
>
>
> Any special reason to use lvm2 from the year 2006 in the year 2013 ?
>

Yes. It is from a specific version of an OS we tested as being stable back
in the day, which unfortunately uses older software such as this LVM
version. It wasn't until recently that I wanted to start using LVM.

> There is no big point in fixing some particular bugs any many years
> obsoleted source code.
>
> Can you try to use/rebuild more recent version?
>

I realize trying a more recent version would be the best thing to do
assuming it would be easy (in this situation it would be a big hassle) but
I was hoping someone could tell me either "yes over allocating to the
snapshot could cause this" or  "it sounds like a bug in that version"
before I go through all that trouble.

>
> Zdenek
>
>
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>

-- 

Tyler Gates*
*

*ATS* | Sr. Systems Administrator

Tyler.Gates at ats.coop

*The Power of **One** Software Solution - **OpenOne*

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